Many azo dyes have absorption of various visible lights and have been therefore conventionally utilized as dyes in various fields. These azo dyes have come to be utilized in various fields, for example, coloring of synthetic resins, printing inks, dyes for sublimation type heat-sensitive transfer material, ink jet inks, and color filter dyes. An absorption spectrum is among the important properties required for azo dyes. The hue of a dye has a large influence on the tint, feeling, and the like of a material colored with the dye, and has a large visual effect. Therefore, studies have been made as to the absorption spectrums of dyes, for a long time. A review thereof is described in “Dyes and Pigments” (1982), vol. 3, pp. 123-131, and it has a detailed explanation.
Recently, the mainstream of image recording materials has been shifted to color image materials, and the applications of dyes have also been diversified. Specifically, dyes are often utilized in recording materials for ink jet systems, recording materials for heat-sensitive transfer systems, recording materials for electrophotographic systems, silver halide light-sensitive materials utilizing transfer systems, and printing inks. Color filters are used to record and reproduce a color image, in imaging devices such as CCDs in the case of photographing devices and in LCDs and PDPs in the case of displays. In these color image recording materials and color filters, colorants (dyes and pigments) having three primary colors in the so-called additive color mixing method or subtractive color mixing method are used, to reproduce and record a full-color image. However, the current situation is still in lack of colorant which has absorbing properties enabling the realization of a desirable color reproducing range, and which can stand to various working conditions and environmental conditions, giving a good hue and high fastness. Therefore, there is a strong demand for improvement.
In the meantime, as regards cyan type azo dyes, dyes are known which use benzoisothiazole as the azo part, under the idea that the absorption wavelength can be made longer without using a nitro group (for example, each publication of JP-T-11-500781 (“JP-T” means searched and published International patent publication) and JP-A-2001-201834 (“JP-A” means unexamined published Japanese patent application)). However, the azo dyes used in these patents have insufficient heat resistance and light fastness, and it is therefore desired to further improve these dyes. It is also commonly required that an azo dye used in each application, has absorbing properties desirable in color reproduction, high fastness in working circumstances, and a large molar extinction coefficient.
Conventionally, azo dyes having, as the azo component, an isothiazole condensed with a five- to six-membered heterocycle are disclosed in each publication of JP-A-56-55455, JP-A-60-14243, JP-A-11-125888, and JP-A-2000-280630. Any of these dyes does not have satisfactory hue, fastness, and molecular extinction coefficient. There are also the descriptions on a method of synthesizing azo dyes having, as the azo component, an isothiazole condensed with a six-membered heterocycle, in “Dyes and Pigments” (1982), vol. 3, pp. 123-131. However, these dyes do not have satisfactory hue, molecular extinction coefficient, and the like.
Other and further features and advantages of the invention will appear more fully from the following description, with taken in connection with the accompanying drawings.